30 



APPLIED ENTOMOLOGY 



referred to, which contribute largely to form the new surface of the body 

 in which head, thorax and abdomen are evident, as are also the antennae, 

 legs, stubs of wings and other adult structures. Many of the internal 

 organs of the larva though, were necessary for use till the last moment 

 before it became a pupa. Then too, ths arrangement of the muscles, 

 in the larva, would not be that needed by the adult. Accordingly, most 

 of the internal organs now gradually break down, losing all their earlier 

 form and structure, and new ones to meet the needs of the adult are con- 

 structed to take their place. 



FIG. 33. Different types of pupation, a, pupa obtecta of a moth; b, pupa libera of a beetle; 

 c, puparium of a fly. a and b about natural size; c much enlarged. (Original.) 



During this breaking down and the reconstruction period, the pupa 

 is practically helpless in most cases, hence generally the need for the 

 protecting cocoon or earthen cell it constructs. 



When the structure of the adult insect has been completed, another 

 molt takes place, the pupa skin splitting and setting free the insect. If 

 it was enclosed in a cocoon it now produces a fluid which sufficiently 

 softens the silken threads so that it can push its way out and it escapes or 

 "emerges." It is now soft, its wings are only partly expanded, as in 

 most cases there would be no room for full-sized wings in a pupa, and 

 because of its reconstruction there is considerable waste matter in its 

 body. The insect crawls upon whatever it may find to hold on to, expels 

 the waste matter, and its wings begin to grow rapidly. Drying out also 

 takes place and in a short time (a few hours) the adult thus produced is 

 in every way fully matured. 



To summarize the differences in metamorphosis of the three groups it 

 may be said that in the Ametabola the insect hatches from the egg prac- 

 tically in an adult condition, i.e., there is little or no metamorphosis. In 

 the Hemimetabola the insect hatches from the egg in a form somewhat 

 resembling the adult but much smaller. It becomes adult by alternating 



